The present invention relates to waveform generators and, more particularly, to a novel circuit for generating a polyphase waveform.
Many uses for a polyphase reference generator exist. For example, in an electric vehicle, a polyphase (typically three-phase) AC generator may be utilized to excite a motor providing power to the driven wheels; selection of vehicle forward and reverse directions is controlled by the phase relationship of the polyphase driving waveforms. Vehicle acceleration and velocity are controlled by the polyphase signal frequency and amplitude. Thus, while the actual motor current, provided by a battery and the like, may be controlled by high-current-flow solid-state devices, the driving signals for the solid-state devices must be provided by a polyphase reference generator; the frequency, phase and amplitude of the polyphase signal must be controllably provided to the desired degree of accuracy. To provide maximum reliability concurrent with minimum costs and volume occupied by the reference generator, it is highly desirable to minimize the number of circuit elements.